ABSTRACT
Recent evidence suggests obesity as a low or systemic chronic inflammation. (Pre)adipocytes in the adipose tissue (AT) express and secrete a variety of cytokines and adipokines. Inducible nitric oxide synthase (iNOS) is an inflammatory enzyme involved in the production of NO. Until now, the inducer(s) of iNOS expression in (pre)adipocytes remains unclear. In this study, we investigated the effects of proinflammatory cytokines (interleukin-1β (IL-1β), IL-10, IL-12, interferon-γ (IFN-γ), adipokines (retinol-binding protein 4 (RBP4), adiponectin, leptin, and resistin), and lipopolysaccharide (LPS), a bacterial cell wall component, on the expression of iNOS in 3T3-L1 preadipocytes. Notably, treatment with IL-1β at 20 ng/mL for 4 h markedly increased iNOS mRNA expression in 3T3-L1 preadipocytes, but that with IL-10 (10 ng/mL), IL-12 (5 ng/mL), IFN-γ (10 ng/mL), RBP4 (5 g/mL), adiponectin (100 ng/mL), leptin (100 ng/mL), and resistin (100 ng/mL), and LPS (1 g/mL) for 4 h had little or no effect on it. Results of dose-response and time-course experiments confirmed the ability of IL-1β at 20 ng/mL for 4 h to maximally induce iNOS mRNA expression in 3T3-L1 preadipocytes. Importantly, pharmacological inhibition studies demonstrated that treatment with AG490 (an inhibitor of Janus-activated kinases (JAKs) and signal transducer and activator of transcription proteins (STATs)), GO6976 (an inhibitor of PKCs), or PP1 (an Src kinase inhibitor) suppressed IL-1β-induced iNOS mRNA expression in 3T3-L1 preadipocytes, pointing out the involvement of JAKs/STATs, PKCs, and Src in the process. This work advocates that IL-1β is a major pro-inflammatory cytokine contributing to inflammation in the AT by up-regulating iNOS.
ABSTRACT
Recent evidence suggests obesity as a low or systemic chronic inflammation. (Pre)adipocytes in the adipose tissue (AT) express and secrete a variety of cytokines and adipokines. Inducible nitric oxide synthase (iNOS) is an inflammatory enzyme involved in the production of NO. Until now, the inducer(s) of iNOS expression in (pre)adipocytes remains unclear. In this study, we investigated the effects of proinflammatory cytokines (interleukin-1β (IL-1β), IL-10, IL-12, interferon-γ (IFN-γ), adipokines (retinol-binding protein 4 (RBP4), adiponectin, leptin, and resistin), and lipopolysaccharide (LPS), a bacterial cell wall component, on the expression of iNOS in 3T3-L1 preadipocytes. Notably, treatment with IL-1β at 20 ng/mL for 4 h markedly increased iNOS mRNA expression in 3T3-L1 preadipocytes, but that with IL-10 (10 ng/mL), IL-12 (5 ng/mL), IFN-γ (10 ng/mL), RBP4 (5 g/mL), adiponectin (100 ng/mL), leptin (100 ng/mL), and resistin (100 ng/mL), and LPS (1 g/mL) for 4 h had little or no effect on it. Results of dose-response and time-course experiments confirmed the ability of IL-1β at 20 ng/mL for 4 h to maximally induce iNOS mRNA expression in 3T3-L1 preadipocytes. Importantly, pharmacological inhibition studies demonstrated that treatment with AG490 (an inhibitor of Janus-activated kinases (JAKs) and signal transducer and activator of transcription proteins (STATs)), GO6976 (an inhibitor of PKCs), or PP1 (an Src kinase inhibitor) suppressed IL-1β-induced iNOS mRNA expression in 3T3-L1 preadipocytes, pointing out the involvement of JAKs/STATs, PKCs, and Src in the process. This work advocates that IL-1β is a major pro-inflammatory cytokine contributing to inflammation in the AT by up-regulating iNOS.
ABSTRACT
Differentiation of preadipocyte, also named adipogenesis, leads to the phenotype of mature adipocyte that is filled with many lipid droplets. Excessive lipid accumulation in adipocytes leads to the development of obesity. In this study, we investigated the effect of 11 different natural compounds on lipid accumulation during the differentiation of 3T3-L1 preadipocytes into 3T3-L1 adipocytes. Strikingly, among the natural compounds, cryptotanshinone at 10 µM most strongly reduced triglyceride (TG) contents in 3T3-L1 cells after 8 days of the differentiation. Furthermore, cryptotanshinone at 10 µM significantly suppressed lipid accumulation in 3T3-L1 cells after 8 days of the differentiation. Cryptotanshinone at 1 to 10 µM tested did not affect the survival of 3T3-L1 cells after 8 days of the differentiation. On mechanistic levels, cryptotanshinone time-differentially decreased the expression levels of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), and perilipin A but also the phosphorylation levels of signal transducer and activator of transcription-3 (STAT-3) during the 3T3-L1 cell differentiation. Taken together, these findings demonstrate that cryptotanshinone inhibits lipid accumulation in differentiating 3T3-L1 cells, which appears to be mediated through the reduced expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, Perilipin A, and STAT-3.
ABSTRACT
Differentiation of preadipocyte, also named adipogenesis, leads to the phenotype of mature adipocyte that is filled with many lipid droplets. Excessive lipid accumulation in adipocytes leads to the development of obesity. In this study, we investigated the effect of 11 different natural compounds on lipid accumulation during the differentiation of 3T3-L1 preadipocytes into 3T3-L1 adipocytes. Strikingly, among the natural compounds, cryptotanshinone at 10 µM most strongly reduced triglyceride (TG) contents in 3T3-L1 cells after 8 days of the differentiation. Furthermore, cryptotanshinone at 10 µM significantly suppressed lipid accumulation in 3T3-L1 cells after 8 days of the differentiation. Cryptotanshinone at 1 to 10 µM tested did not affect the survival of 3T3-L1 cells after 8 days of the differentiation. On mechanistic levels, cryptotanshinone time-differentially decreased the expression levels of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), and perilipin A but also the phosphorylation levels of signal transducer and activator of transcription-3 (STAT-3) during the 3T3-L1 cell differentiation. Taken together, these findings demonstrate that cryptotanshinone inhibits lipid accumulation in differentiating 3T3-L1 cells, which appears to be mediated through the reduced expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, Perilipin A, and STAT-3.
ABSTRACT
Differentiation of preadipocyte, also named adipogenesis, leads to the phenotype of mature adipocyte that is filled with many lipid droplets. Excessive lipid accumulation in adipocytes leads to the development of obesity. In this study, we investigated the effect of 11 different natural compounds on lipid accumulation during the differentiation of 3T3-L1 preadipocytes into 3T3-L1 adipocytes. Strikingly, among the natural compounds, cryptotanshinone at 10 µM most strongly reduced triglyceride (TG) contents in 3T3-L1 cells after 8 days of the differentiation. Furthermore, cryptotanshinone at 10 µM significantly suppressed lipid accumulation in 3T3-L1 cells after 8 days of the differentiation. Cryptotanshinone at 1 to 10 µM tested did not affect the survival of 3T3-L1 cells after 8 days of the differentiation. On mechanistic levels, cryptotanshinone time-differentially decreased the expression levels of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), and perilipin A but also the phosphorylation levels of signal transducer and activator of transcription-3 (STAT-3) during the 3T3-L1 cell differentiation. Taken together, these findings demonstrate that cryptotanshinone inhibits lipid accumulation in differentiating 3T3-L1 cells, which appears to be mediated through the reduced expression and/or phosphorylation levels of C/EBP-α, PPAR-γ, FAS, Perilipin A, and STAT-3.